1. Field of the Invention
The instant disclosure relates to an AC light emitting device; in particular, to an AC light emitting device for illumination.
2. Description of Related Art
The light emitting diode (LED) has low power consumption, high luminosity and long life-time, and thus LED has been widely used in many kinds of lighting devices. The lighting device comprises the rectifying circuit, the switch, the light emitting module and the current source. The light emitting module comprises a plurality of LEDs connected in series. For illustration, the rectifying circuit can be the full-wave rectifying circuit. Thus, the pulse DC current can be obtained after the AC power is rectified via the rectifying circuit, and the pulse DC current is provided as the input power of the LEDs. When the LEDs in series are turned on, the current source can provide a stable current to each LED in the light emitting module.
However, usually the luminosity of the lighting device is switched via the group loop control method, and the switch can turn on, partially turn on or turn off the light emitting module. For example, the user operates the switch once to make the light emitting module turn on, operates the switch twice to make the light emitting module partially turn on, and operates the switch three times to make the light emitting module turn off.
Thus, the above operation may result in various luminosities within the area where the lighting device emits lights. For example, the area where the light emitting module turns on has a high luminosity, but the area where the light emitting module turns off has a low luminosity.
In addition to the above problem, in the case that the light emitting module partially turns on within certain area, some of LEDs are frequently used which result in their shorter lifetime or the risk of being damaged because of the over current.